Known dry-cleaning processes consist of a wash, rinse, and drying cycle with solvent recovery. Garments are loaded into a basket in a cleaning drum and immersed in a dry-cleaning fluid or solvent, which is pumped into the cleaning drum from a base tank. Conventional dry-cleaning fluids include perchloroethylene (PCE), petroleum-based or Stoddard solvents, CFC-113, and 1,1,1-trichloroethane, all of which are generally aided by a detergent. The solvent is used to dissolve soluble contaminants, such as oils, and to entrain and wash away insoluble contaminants, such as dirt.
The use of these conventional solvents, however, poses a number of health and safety risks as well as being environmentally hazardous. For example, halogenated solvents are known to be environmentally unfriendly, and at least one of these solvents, PCE, is a suspected carcinogen. Known petroleum-based solvents are flammable and can contribute to the production of smog. Accordingly, dry cleaning systems which utilize dense phase fluids, such as liquid carbon dioxide, as a cleaning medium have been developed. An apparatus and method for employing liquid carbon dioxide as the dry-cleaning solvent is disclosed in U.S. Pat. No. 5,467,492, entitled "Dry-Cleaning Garments Using Liquid Carbon Dioxide Under Agitation As Cleaning Medium". A similar dry cleaning apparatus is also disclosed in U.S. Pat. No. 5,651,276.
These systems pose a number of other problems, particularly in relation to the high operating pressures necessary for maintaining the gas in a liquid state. For example, the various pressurized components of the system must be constructed with thick, heavy walled structures to withstand the elevated pressures encountered during the dry cleaning operation. These bulky structures can consume a significant amount of space if they are not carefully laid out. However, in order to encourage dry cleaning operators to convert to liquid carbon dioxide dry cleaning systems, these new systems must be configured so as to minimize space consumption. This is necessary to enable such systems to be placed into facilities and locations designed for existing dry-cleaning equipment. Moreover, due to the neighborhood nature of many dry cleaning operations, there can be even greater space limitations. Thus, while minimizing space requirements is always an important object, it is particularly important with dry cleaning equipment.
In terms of space consumption, one of the more critical aspects of a liquid carbon dioxide dry cleaning apparatus is the area required for opening and closing of the door of the pressurized cleaning vessel to permit loading and removal of garments or other items. Since the cleaning vessel in a liquid carbon dioxide system operates at a high pressure (e.g. 500-850 psi) under ambient temperature conditions in order to ensure that the carbon dioxide remains in a liquid phase, a relatively bulky, heavy walled door must be used. One type of door which could be used on such a liquid carbon dioxide cleaning vessel is a conventional hinged door. Due to the weight of the door, an opening mechanism typically would have to be provided for swinging the door to an open position at the side of the cleaning vessel. However, with such a hinged door a significant amount of clearance would have to be provided both in front of the cleaning vessel, to allow for the swinging motion of the door, and to at least one side of the cleaning vessel. Moreover, additional space would have to be provided for the door opening and closing mechanism.
The need to provide clearance in the front of the cleaning vessel could be eliminated by using a door which could slide horizontally into an open position, however once again clearance would have to provided on at least one side of the cleaning vessel to allow for the open door. Additionally, the mechanism for horizontally sliding the door to the open position would have to be arranged to the side of the cleaning vessel and likely would require additional space.